package com.zhangyong.DataStructures.Tree.AVL;

import java.util.ArrayList;

/**
 * <p>ClassName:  </p>
 * <p>Description: 平衡二叉树 </p>
 * 在BST基础上添加 自平衡机制;
 *
 * @author zhangyong
 * @version 1.0.0
 * @date 2018/12/13 15:06
 */
public class AVLTree<K extends Comparable<K>, V> {
    private class Node {
        public K key;
        public V value;
        public Node left, right;
        public int height;

        public Node(K key, V value) {
            this.key = key;
            this.value = value;
            left = null;
            right = null;
            height = 1;
        }
    }

    private Node root;
    private int size;

    public AVLTree() {
        root = null;
        size = 0;
    }

    public int getSize() {
        return size;
    }

    public boolean isEmpty() {
        return size == 0;
    }

    //判断二叉树是否是一颗二分搜索树
    private boolean isBST() {
        ArrayList<K> keys = new ArrayList<>();
        inOrder(root, keys);
        for (int i = 1; i < keys.size(); ++i) {
            if (keys.get(i - 1).compareTo(keys.get(i)) > 0) {
                return false;
            }
        }
        return true;
    }

    /**
     * 中序遍历
     *
     * @param node
     * @param keys
     */
    private void inOrder(Node node, ArrayList<K> keys) {
        if (node == null) {
            return;
        }
        inOrder(node.left, keys);
        keys.add(node.key);
        inOrder(node.right, keys);
    }

    //判断一颗二叉树是不是平衡二叉树
    public boolean isBalanced() {
        return isBalanced(root);
    }

    /**
     * 判断一颗二叉树是否是一颗平衡二叉树
     *
     * @param node
     * @return
     */
    private boolean isBalanced(Node node) {
        if (node == null) {
            return true;
        }
        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor) > 1) {
            return false;
        }
        return isBalanced(node.left) && isBalanced(node.right);
    }

    // 向二分搜索树中添加新的元素(key, value)
    public void add(K key, V value) {
        root = add(root, key, value);
    }

    //获取高度;
    //叶子节点高度为0，非叶子节点高度为左右孩子节点最大+1
    private int getHeight(Node node) {
        if (node == null) {
            return 0;
        }
        return node.height;
    }

    // 向以node为根的二分搜索树中插入元素(key, value)，递归算法
    // 返回插入新节点后二分搜索树的根
    private Node add(Node node, K key, V value) {
        if (node == null) {
            size++;
            return new Node(key, value);
        }
        if (key.compareTo(node.key) < 0) {
            node.left = add(node.left, key, value);
        } else if (key.compareTo(node.key) > 0) {
            node.right = add(node.right, key, value);
        } else if (key.compareTo(node.key) == 0) {
            node.value = value;
        }
        //添加节点之后 更新当前node的height
        node.height = Math.max(getHeight(node.left), getHeight(node.right)) + 1;
        //计算 平衡因子
        int balanceFactor = getBalanceFactor(node);
        if (Math.abs(balanceFactor) > 1) {
            System.out.println("This tree is unbalanced, the unbalanced coefficient is :" + balanceFactor);
        }
        //平衡维护
        //【1】LL
        /**
         *             a                   b
         *           /  \               /     \
         *          b    c ===>        d       a
         *        /  \               /       /  \
         *       d   e              f       e    c
         *     /
         *    f
         */
        if (balanceFactor > 1 && getBalanceFactor(node.left) >= 0) {
            return rightRotate(node);
        }
        //【2】RR
        /**
         *             a                       c
         *           /  \                    /   \
         *          b    c     ===>         a    e
         *             /  \               /  \    \
         *            d    e             b   d     f
         *                 \
         *                 f
         */
        if (balanceFactor < -1 && getBalanceFactor(node.right) <= 0) {
            return leftRotate(node);
        }
        //【3】LR
        /**
         *             a                         a                         e
         *           /  \                     /     \                   /     \
         *          b    c      ===>         e       c    ===>         b        a
         *        /  \                     /   \                    /    \    /   \
         *       d    e                   b     h                  d     g   h     c
         *          /  \                /   \
         *         g   h              d     g
         */
        if (balanceFactor > 1 && getBalanceFactor(node.left) < 0) {
            node.left = leftRotate(node.left);
            return rightRotate(node.left);
        }
        // 【4】 RL
        if (balanceFactor < -1 && getBalanceFactor(node.right) > 0) {
            node.right = rightRotate(node.right);
            return leftRotate(node.right);
        }
        return node;
    }

    /**
     * 右旋转
     * // 对节点y进行向右旋转操作，返回旋转后新的根节点x
     * //        y                              x
     * //       / \                           /   \
     * //      x   T4     向右旋转 (y)        z     y
     * //     / \       - - - - - - - ->    / \   / \
     * //    z   T3                       T1  T2 T3 T4
     * //   / \
     * // T1   T2
     * 节点 y 即为开始不平衡的点;
     *
     * @param y
     * @return
     */
    private Node rightRotate(Node y) {
        Node x = y.left;
        Node T3 = x.right;
        //向右旋转过程;
        x.right = y;
        y.left = T3;
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;
        return x;
    }

    /**
     * 左旋转
     * // 对节点y进行向右旋转操作，返回旋转后新的根节点x
     * //        y                              x
     * //       / \                           /    \
     * //      T4 x     向左旋转 (y)          y      z
     * //        / \                        / \    /  \
     * //      T3  z                      T4  T3  T2  T1
     * //          / \
     * //        T2 T1
     * 节点 y 即为开始不平衡的点;
     *
     * @param y
     * @return
     */
    private Node leftRotate(Node y) {
        Node x = y.right;
        Node T3 = x.left;
        x.left = y;
        y.right = T3;
        y.height = Math.max(getHeight(y.left), getHeight(y.right)) + 1;
        x.height = Math.max(getHeight(x.left), getHeight(x.right)) + 1;
        return x;
    }

    //获取一个节点的平衡因子
    private int getBalanceFactor(Node node) {
        if (node == null)
            return 0;
        return getHeight(node.left) - getHeight(node.right);
    }

    // 返回以node为根节点的二分搜索树中，key所在的节点
    private Node getNode(Node node, K key) {
        if (node==null) {
            return null;
        }
        if (key.equals(node.key))
            return node;
        else if (key.compareTo(node.key) < 0)
            return getNode(node.left, key);
        else // if(key.compareTo(node.key) > 0)
            return getNode(node.right, key);
    }

    public boolean contains(K key) {
        return getNode(root, key) != null;
    }

    public V get(K key) {

        Node node = getNode(root, key);
        if (node == null) {
            return null;
        }
        return node.value;
    }

    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (node == null)
            throw new IllegalArgumentException(key + " doesn't exist!");

        node.value = newValue;
    }

    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node minimum(Node node) {
        if (node.left == null)
            return node;
        return minimum(node.left);
    }

    // 删除掉以node为根的二分搜索树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    private Node removeMin(Node node) {

        if (node.left == null) {
            Node rightNode = node.right;
            node.right = null;
            size--;
            return rightNode;
        }

        node.left = removeMin(node.left);
        return node;
    }

    // 从二分搜索树中删除键为key的节点
    public V remove(K key) {

        Node node = getNode(root, key);
        if (node != null) {
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    private Node remove(Node node, K key) {

        if (node == null)
            return null;

        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            return node;
        } else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            return node;
        } else {   // key.compareTo(node.key) == 0

            // 待删除节点左子树为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }

            // 待删除节点右子树为空的情况
            if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }

            // 待删除节点左右子树均不为空的情况

            // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置
            Node successor = minimum(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;

            node.left = node.right = null;

            return successor;
        }
    }

    public static void main(String[] args) {

        System.out.println("Pride and Prejudice");

        ArrayList<String> words = new ArrayList<>();
        if (FileOperation.readFile("pride-and-prejudice.txt", words)) {
            System.out.println("Total words: " + words.size());

            AVLTree<String, Integer> map = new AVLTree<>();
            for (String word : words) {
                if (map.contains(word))
                    map.set(word, map.get(word) + 1);
                else
                    map.add(word, 1);
            }

            System.out.println("Total different words: " + map.getSize());
            System.out.println("Frequency of PRIDE: " + map.get("pride"));
            System.out.println("Frequency of PREJUDICE: " + map.get("prejudice"));

            System.out.println("is BST ：" + map.isBST());
        }

        System.out.println();
    }
}
